---

yaml
---
r: 125031
b: refs/heads/master
c: 1f8f1e2
h: refs/heads/master
i:
  125029: e21eb27
  125027: 15f7039
  125023: 88c056f
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e4adca27bcbb8a73c4cf1dfa71392654cfa33345
+refs/heads/master: 1f8f1e296583f9f832c2fe7b5a219675b74bf43e

trunk/fs/devpts/inode.c

@@ -27,6 +27,13 @@
 #define DEVPTS_SUPER_MAGIC 0x1cd1
 
 #define DEVPTS_DEFAULT_MODE 0600
+/*
+ * ptmx is a new node in /dev/pts and will be unused in legacy (single-
+ * instance) mode. To prevent surprises in user space, set permissions of
+ * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful
+ * permissions.
+ */
+#define DEVPTS_DEFAULT_PTMX_MODE 0000
 #define PTMX_MINOR	2
 
 extern int pty_limit;			/* Config limit on Unix98 ptys */
@@ -40,23 +47,28 @@ struct pts_mount_opts {
 	uid_t   uid;
 	gid_t   gid;
 	umode_t mode;
+	umode_t ptmxmode;
 };
 
 enum {
-	Opt_uid, Opt_gid, Opt_mode,
+	Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode,
 	Opt_err
 };
 
 static const match_table_t tokens = {
 	{Opt_uid, "uid=%u"},
 	{Opt_gid, "gid=%u"},
 	{Opt_mode, "mode=%o"},
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+	{Opt_ptmxmode, "ptmxmode=%o"},
+#endif
 	{Opt_err, NULL}
 };
 
 struct pts_fs_info {
 	struct ida allocated_ptys;
 	struct pts_mount_opts mount_opts;
+	struct dentry *ptmx_dentry;
 };
 
 static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
@@ -81,6 +93,7 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts)
 	opts->uid     = 0;
 	opts->gid     = 0;
 	opts->mode    = DEVPTS_DEFAULT_MODE;
+	opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
 
 	while ((p = strsep(&data, ",")) != NULL) {
 		substring_t args[MAX_OPT_ARGS];
@@ -109,6 +122,13 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts)
 				return -EINVAL;
 			opts->mode = option & S_IALLUGO;
 			break;
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+		case Opt_ptmxmode:
+			if (match_octal(&args[0], &option))
+				return -EINVAL;
+			opts->ptmxmode = option & S_IALLUGO;
+			break;
+#endif
 		default:
 			printk(KERN_ERR "devpts: called with bogus options\n");
 			return -EINVAL;
@@ -118,12 +138,93 @@ static int parse_mount_options(char *data, struct pts_mount_opts *opts)
 	return 0;
 }
 
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+static int mknod_ptmx(struct super_block *sb)
+{
+	int mode;
+	int rc = -ENOMEM;
+	struct dentry *dentry;
+	struct inode *inode;
+	struct dentry *root = sb->s_root;
+	struct pts_fs_info *fsi = DEVPTS_SB(sb);
+	struct pts_mount_opts *opts = &fsi->mount_opts;
+
+	mutex_lock(&root->d_inode->i_mutex);
+
+	/* If we have already created ptmx node, return */
+	if (fsi->ptmx_dentry) {
+		rc = 0;
+		goto out;
+	}
+
+	dentry = d_alloc_name(root, "ptmx");
+	if (!dentry) {
+		printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n");
+		goto out;
+	}
+
+	/*
+	 * Create a new 'ptmx' node in this mount of devpts.
+	 */
+	inode = new_inode(sb);
+	if (!inode) {
+		printk(KERN_ERR "Unable to alloc inode for ptmx node\n");
+		dput(dentry);
+		goto out;
+	}
+
+	inode->i_ino = 2;
+	inode->i_uid = inode->i_gid = 0;
+	inode->i_blocks = 0;
+	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+
+	mode = S_IFCHR|opts->ptmxmode;
+	init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2));
+
+	d_add(dentry, inode);
+
+	fsi->ptmx_dentry = dentry;
+	rc = 0;
+
+	printk(KERN_DEBUG "Created ptmx node in devpts ino %lu\n",
+			inode->i_ino);
+out:
+	mutex_unlock(&root->d_inode->i_mutex);
+	return rc;
+}
+
+static void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+	struct inode *inode;
+	if (fsi->ptmx_dentry) {
+		inode = fsi->ptmx_dentry->d_inode;
+		inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode;
+	}
+}
+#else
+static inline void update_ptmx_mode(struct pts_fs_info *fsi)
+{
+       return;
+}
+#endif
+
 static int devpts_remount(struct super_block *sb, int *flags, char *data)
 {
+	int err;
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 	struct pts_mount_opts *opts = &fsi->mount_opts;
 
-	return parse_mount_options(data, opts);
+	err = parse_mount_options(data, opts);
+
+	/*
+	 * parse_mount_options() restores options to default values
+	 * before parsing and may have changed ptmxmode. So, update the
+	 * mode in the inode too. Bogus options don't fail the remount,
+	 * so do this even on error return.
+	 */
+	update_ptmx_mode(fsi);
+
+	return err;
 }
 
 static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
@@ -136,6 +237,9 @@ static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
 	if (opts->setgid)
 		seq_printf(seq, ",gid=%u", opts->gid);
 	seq_printf(seq, ",mode=%03o", opts->mode);
+#ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES
+	seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode);
+#endif
 
 	return 0;
 }
@@ -156,14 +260,15 @@ static void *new_pts_fs_info(void)
 
 	ida_init(&fsi->allocated_ptys);
 	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
+	fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE;
 
 	return fsi;
 }
 
 static int
 devpts_fill_super(struct super_block *s, void *data, int silent)
 {
-	struct inode * inode;
+	struct inode *inode;
 
 	s->s_blocksize = 1024;
 	s->s_blocksize_bits = 10;
@@ -190,7 +295,7 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
 	s->s_root = d_alloc_root(inode);
 	if (s->s_root)
 		return 0;
-	
+
 	printk("devpts: get root dentry failed\n");
 	iput(inode);
 
@@ -211,7 +316,7 @@ static void devpts_kill_sb(struct super_block *sb)
 	struct pts_fs_info *fsi = DEVPTS_SB(sb);
 
 	kfree(fsi);
-	kill_anon_super(sb);
+	kill_litter_super(sb);
 }
 
 static struct file_system_type devpts_fs_type = {